|
Post by orrum on Jun 18, 2015 8:36:47 GMT -5
Hopefully this is in the right section.
I want to core drill a hole in a cab preform and then core drill opal and put it in the hole in the preform and of course glue it. I presume I would use 330 epoxy?
Next is if I drill the opal slab with a core drill then I think I would have to use a bigger core drill to drill the hole in the preform so that the opal core would fit? So what is the differential in between the two core drills?
I will be using like hardness preform and opal so that it won't undercut as I cab it.
Thanks and as always if you have pictures of this I would appreciate you posting!
|
|
herb
spending too much on rocks
Member since November 2011
Posts: 445
|
Post by herb on Jun 18, 2015 9:47:40 GMT -5
I can't really help answer your question. The inside diameter of the bit you use for the opal needs to match the outside diameter of the bit you use for the preform, so the bigger bit would be for the opal. I've never looked that carefully, but I've only seen core bits sold by their outside diameters. They might be available as matched innie-outie sets though. If not, you might end up having to cut the opal a bit large and then carefully grind it down to fit the preform.
Even if you did find core bits where the inside diameter of one matches the outside diameter of the other, I think I'd still opt to cut the opal large and then trim it down because any little bit of movement while drilling could make for a sloppy fit.
|
|
minerken
Cave Dweller
Member since August 2013
Posts: 466
|
Post by minerken on Jun 18, 2015 18:51:23 GMT -5
I have considerable experience with coring bits although in another life as I am retired. Core bits are just that a hollow centred bit designed to create and recover a core. In lapidary work they are generally used for the hole not the core so you would want the O.D. but for core recovery yes you want the inside dimensions and this is what a bit advertised as a core bit should be. Why would you want a core? Well in your case you want to use it for an intarsia piece of jewellery but rock cores are cut and retrieved for scientific purposes, Geologists use the cores to investigate property's of a rock you can use your imagination as to the stories the core can tell, What are the minerals in a section of rock, gold, copper, silver, or fossils,the mechanical properties like the shear strength, hardness. This information can tell them if a mine-able deposit, an oil field, or just a different type of rock things that may be used by a collage to develop geological theories. Ok enough of that, back to your question a core bit is not a precise tool it will wear unevenly due to different rock hardness etc and after the diamond wore down a thousandth or so the next cut would be to big for your piece, now with very soft rock like your opal you may be able to get by with it a little longer assuming it was precise the first time. The only way I can think of to do this would be with a rock lath and precision milling tools.
|
|
|
Post by orrum on Jun 19, 2015 6:38:38 GMT -5
Thanks for the info. I was hoping for a easy way to do this. I guess the way to go is drill the insert piece bigger and grind it down to fit. The reason that worries me is keeping it round.
|
|
NDK
Cave Dweller
Member since January 2009
Posts: 9,440
|
Post by NDK on Jun 19, 2015 14:12:28 GMT -5
There was a guy on here a few years ago doing just as you're questioning. I forget who it was, but do remember the difficulty he had matching the plug to the hole bored out of the cab.
Maybe someone else here remembers, would be good to go back & see his work & if he posted his trials & tribulations.
|
|
|
Post by rockpickerforever on Jun 19, 2015 14:25:19 GMT -5
|
|
minerken
Cave Dweller
Member since August 2013
Posts: 466
|
Post by minerken on Jun 19, 2015 14:38:12 GMT -5
On the other forum they have an intarsia section where I found linkI think he was just using a dremel.
|
|
|
Post by orrum on Jun 19, 2015 17:15:48 GMT -5
Wow good threads, thanks for listing them!
|
|
|
Post by Rockoonz on Jun 19, 2015 18:12:51 GMT -5
The woman who taught me intarsia uses an old faceter to cut her inserts perfectly round, she sets the mast to parallel to the lap and turns the dop to make it round the same way a faceter rounds out his preform. For a regular grinder you could glue your preform securely to a nail, chuck the nail into a drill motor, and run the drill on a slow speed while grinding to size. Some intarsia cutters put colored pigments in their glue to help hide glue joints, you can get them at Tap Plastics.
|
|